OBJECTIVES: 1. Development of a clinically useful, reliable, and safe test to measurethe severity of atherosclerosis. Purified lipid stains, or other lipophilic or cholesterophilic materials, will be tagged with radioisotope and injected into the lumen of an artery between tourniquets. The radio-activity retained after tourniquet release, and its rate of washout from the artery wall will be measured by external detectors, and the curve used to calculate the extent of underlying fatty arterial lesions in animals. The excised artery will be analyzed for lipids for correlation. Local radiation and toxic effects will be studied. 2. Human radial artery trials will be made, using postmortem and clinical atherosclerosis to correlate with the test. 3. The test will then be used to evaluate in months to a few years various drug, diet and exercise treatments now requiring decades to assess. Use of a sensitive test on a peripheral artery not subject to the marked local variations in disease that proximal and coronary vessels display will give a better insight into the general metabolic arterial changes. Objectives 2 and 3 are the projected aims of future proposals.